1. Technical Field
The present invention relates to an apparatus for fabricating a semiconductor device, and more particularly, to an apparatus for fabricating a liquid crystal display device.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device includes a first substrate and a second substrate separated from each other by having a liquid crystal layer interposed therebetween, wherein the first substrate has a black matrix, a color filter layer including red, green and blue sub-color filters and a common electrode, and the second substrate has a switching element and a pixel electrode. When a voltage is supplied to the common electrode and the pixel electrode, an electric field is generated that changes the orientation of liquid crystal molecules of the liquid crystal layer due to optical anisotropy within the liquid crystal layer. Consequently, light transmittance characteristics of the liquid crystal layer are modulated and images are displayed by the LCD device.
Recently, an active matrix type LCD device has become widely used where a plurality of pixel regions are disposed in matrix and a switching element, such as a thin film transistor (TFT), is formed in each pixel region. The TFT is fabricated through the repetition of thin film-forming steps and photolithographic processes for the thin films including a photoresist-patterning step and a thin film-etching step.
The thin film-forming and thin film-etching steps are performed in an isolated vacuum space using reaction gases. An apparatus including a chamber is used for the thin film-forming and thin film etching steps, where a substrate is disposed in the chamber defining a vacuum reaction space isolated from the exterior surroundings. An apparatus including a chamber may be classified into two types according to the method of supplying and distributing reaction gases into a chamber: a shower head type and a side flow type. In a shower head type apparatus, the reaction gases are supplied into a top portion of the chamber and flow downwardly though the chamber to a bottom portion of the chamber. In a side flow type apparatus, the reaction gases are supplied into one side portion of the chamber and laterally flow over a substrate to the other side portion of the chamber.
FIG. 1 is a schematic cross-sectional view showing a side flow type apparatus including a chamber according to the related art. In FIG. 1, a side flow type apparatus includes a chamber 10, an upper electrode 20 and a lower electrode 30. The chamber 10 is a vacuum reaction space isolated from the exterior surroundings, and the upper and lower electrodes 20 and 30 are disposed in the chamber 10. The upper and lower electrodes 20 and 30 face each other with a substrate 2 disposed therebetween. The upper electrode 20 includes a backing plate 22, which functions as one electrode for generating and maintaining a plasma. The lower electrode 30 includes a susceptor 32, which functions as the other electrode for generating and maintaining the plasma. Radio frequency (RF) power is applied between the upper and lower electrodes 20 and 30. In addition, the lower electrode 30 functions as a chuck supporting the substrate 2.
An injection slit 12 and an exhaust slit 14 are formed through a sidewall of the chamber 10. The injection slit 12 and the exhaust slit 14 face each other and the substrate 2 is disposed between the injection slit 12 and the exhaust slit 14. The injection slit 12 and the exhaust slit 14 are horizontally disposed. Reaction gases supplied to the chamber are injected into the chamber 10 through the injection slit 12 and flow along a top surface of the substrate 2 and are exhausted out of the chamber 10 through the exhaust slit 14. For the above-mentioned flow path of the reaction gases, the injection slit 12 is connected to a gas supply system through an inlet pipe 16 and the exhaust slit 14 is connected to a vacuum system such as a pump through an output pipe 18.
After the substrate 2 is transferred into the chamber 10 and loaded on the susceptor 32, the RF power is applied between the backing plate 22 and the susceptor 32, and the reaction gases are injected into the chamber 10 through the injection slit 12. The injected reaction gases are excited due to the RF power form a plasma. As a result, a thin film may be formed on the substrate 2 by the plasma or a thin film on the substrate 2 may be etched by the plasma. During the plasma treatment process, the reaction gases are continuously exhausted out of the chamber 10 through the exhaust slit 14 to maintain a vacuum condition of the chamber 10.
FIG. 2 is a schematic perspective view showing a side flow type apparatus including a chamber according to the related art. In FIG. 2, the injection slit 12 and the exhaust slit 14 facing each other is formed through the sidewall of the chamber 10. The injection slit 12 and the exhaust slit 14 are horizontally disposed with a height of about 2 mm.
In the side flow type apparatus having the injection slit 12 and the exhaust slit 14, however, since the injection slit 12 and the exhaust slit 14 are disposed in local places in the chamber 10, a pressure of the reaction gases varies with position in the chamber 10. The variation of the pressure of the reaction gases causes a variation in amount of injected gases and in amount of exhausted gases, thereby causing a non-uniformity in the plasma treatment process. For example, a film is not uniformly deposited on the substrate 2 or a film on the substrate 2 is not uniformly etched.
As referring again to FIGS. 1 and 2, the reaction gases are supplied to the chamber 10 through the inlet pipe 16. Since the inlet pipe 16 has a width narrower than the injection slit 12, the reaction gases are abruptly diffused into chamber 10 at the injection slit 12. Accordingly, the reaction gases are not uniformly distributed in the chamber 10 and the pressure of the distributed reaction gases varies with position in the chamber 10. As a result, the amount of the distributed reaction gases varies with position in the chamber, which causes a non-uniformity in the plasma treatment process.
Similarly, since the processed reaction gases are evacuated through the outlet pipe 18 having a width narrower than the exhaust slit 14, the processed reaction gases are abruptly concentrated into the exhaust slit 14. Accordingly, the processed reaction gases are not uniformly evacuated from the chamber 10 and the pressure variation of the reaction gas with position in the chamber 10 is enlarged. As a result, the variation in the amount of the reaction gases and the non-uniformity in the plasma treatment process increases. The non-uniformity in the plasma treatment process results in deterioration of the thin film and causes deterioration in display quality of the LCD device.